The AU-rich sequences in the 3' untranslated region mediate the increased turnover of interferon mRNA induced by glucocorticoids.

Abstract

SummaryDifferent vectors were constructed that expressed the human interferon-0 (IFN-0) mRNA constitutively and contained various deletions in the 3' untranslated region (UTR). AU-rich sequences in the 3' UTR were specifically deleted in two vectors . Cell lines secreting human IFN-O were established by transfecting murine L929 cells with the vectors . These cells showed similar levels of IFN-,Q mRNA and secreted comparable amounts of IFN-,13, indicating that the deletion of AU-rich sequences had no effect on the stability and little effect on the efficiency of translation ofthis mRNA. The synthetic glucocorticoid dexamethasone was previously shown to increase the turnover of IFN-O mRNA. This activity of dexamethasone was clearly observed only in cells expressing IFN-O mRNA with AU-rich sequences in the 3' UTR . The increased turnover of this mRNA occurred in the presence of cycloheximide; therefore, it did not require synthesis of new proteins. These findings suggest that glucocorticoids may activate a ribonuclease that degrades mRNAs containing AU-rich sequences in the 3' UTR.G lucocorticoids regulate gene expression in different ways.When these hormones bind to cytoplasmic receptors, glucocorticoid-receptor complexes translocate into the nucleus where they bind to target DNA sequences with high affinity (see reference 1 for a review) . This binding is a primary response that does not require protein synthesis and either stimulates or represses gene transcription (1), as it has been shown for ot-fetoprotein (2) and proopiomelanocortin (3) . Glucocorticoids can also modulate gene expression posttranscriptionally. For example, the stability offibronectin (4) and human growth hormone mRNA is enhanced by glucocorticoid treatment (5) ; concomitantly, the length of the poly(A) tail of this mRNA is increased (6) . Moreover, the mRNA for phosphoenolpyruvate carboxykinase contains a a glucocorticoid-responsive stabilizing element (7) . In contrast, the glucocorticoids inhibit the synthesis of certain cytokines and ofother proteins post-transcriptionally. Treatment with the synthetic glucocorticoid dexamethasone (DEX)' has been shown to destabilize the mRNA for IIAO (8), type 1 procollagen (9) and 3-hydroxy-3-methylglutarylcoenzyme A reductase (10). In addition, DEX inhibits the 'Abbreviations used in this payer: AU elements, AU-rich sequences in the 3' untranslated region; DEX, dexamethasone; GAPDH, glyceraldehyde 3-phosphate dehydrogenase ; GM-CSF, granulocyte-monocyte colonystimulating factor; TE, 10 mm Tris-HO, pH 7 .5, 1 mM EDTA; tk, herpes simplex virus thymidine kinase gene ; UTR, untranslated region . synthesis of T cell growth factor and the accumulation of IFN -,y mRNA in phytohemoagglutinin-stimulated lymphocytes (11), and decreases the level of nerve growth factor mRNA in L929 cells (12).Treatment with glucocorticoids inhibits production of IFN and increases the lethality of Coxsackie virus in infected mice (13)(14) . DEX decreases IFN production (15) and increases the turnover of IFN-O mRNA in human fibrobl...

Association of novel polymorphisms with the expression of SPARC in normal fibroblasts and with susceptibility to scleroderma

“…It is believed that the 3Ј-UTR may play important roles in mRNA stability. For instance, a cluster of 3 SNPs in the 3Ј-UTR of human plasma cell membrane glycoprotein 1 (PC-1) is associated with stabilization of PC-1 mRNA and increased PC-1 protein content (32); a conserved AU sequence from the 3Ј-UTR of granulocyte macrophage colony-stimulating factor or interferon-␤ mRNA mediates selective mRNA degradation (33,34). Our functional studies of the SPARC SNPs indicated that SNP ϩ998 may affect SPARC mRNA stability.…”

Anti-inflammatory functions of glucocorticoid-induced genes

“…Targets of such regulation include COX-2 (Chivers et al, 2006;Lasa et al, 2001;Newton et al, 1998;Ristimaki et al, 1996), TNF (Han et al, 1990;Kontoyiannis et al, 1999;Swantek et al, 1997), vascular endothelial growth factor (Gille et al, 2001), interferon β (Peppel et al, 1991), colony stimulating factor 2 (CSF2) (Bergmann et al, 2004;Tobler et al, 1992;Tran et al, 2005), IL-5 (Staples et al, 2003), IL-6 (Amano et al, 1993;Tobler et al, 1992), IL-1α and -1β (Amano et al, 1993;Lee et al, 1988), inducible nitric oxide synthase (Korhonen et al, 2002) and several chemokines (Berkman et al, 1995;Brach et al, 1992;Chang et al, 2001;Chaudhary and Avioli, 1996;Chivers et al, 2006;Mukaida et al, 1991;Poon et al, 1999;Stellato et al, 1999;Tobler et al, 1992). The majority of these mRNAs have in common the presence of adenylate/uridylate-rich elements (AREs) in their 3' untranslated regions (UTRs).…”

The interferon gene cluster: a candidate region for MS predisposition?

“…22 Since the IFNB gene lacks introns and the unprocessed precursor is not more than 187 aa in length, three primer pairs (Table 1) were sufficient to screen the 5'UTR (368 bp), 3′UTR (327 bp) and the coding region (561 bp) for polymorphism by SSCP analysis (IFNB AC# J00218). A single C → T transition was identified at nucleotide (nt) 153, leaving the aa tyrosine in position 51 of the unprocessed precursor unchanged [Tyr51Tyr].…”